Water dispersible polyanilines made with polymeric acid colloids for electronics applications

ABSTRACT

Methods are provided to producing stable, aqueous dispersions of polyaniline and colloid-forming polymeric acids. Films from the disclosed compositions are useful as buffer layers, in organic electronic devices including electroluminescent devices, such as organic light emitting diodes (OLED) displays. Films cast from the compositions are also useful in combination with nanometal wires or carbon nanotubes in applications such as drain, source, or gate electrodes in thin film field effect transistors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 10/669,577filed on Sep. 24, 2003, now allowed, which claims priority under 35U.S.C. §119(e) from Provisional Application No. 60/413,203, which isincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The invention relates to aqueous dispersions of electrically conductingpolymers of aniline, wherein the electrically conducting polymer issynthesized in the presence of polymeric acid colloids.

BACKGROUND OF THE INVENTION

Electrically conducting polymers have been used in a variety of organicelectronic devices, including in the development of electroluminescent(EL) devices for use in light emissive displays. With respect to ELdevices, such as organic light emitting diodes (OLEDs) containingconducting polymers, such devices generally have the followingconfiguration:

-   -   anode/buffer layer/EL polymer/cathode        The anode is typically any material that has the ability to        inject holes into the otherwise filled π-band of the        semiconducting, EL polymer, such as, for example, indium/tin        oxide (ITO). The anode is optionally supported on a glass or        plastic substrate. The EL polymer is typically a conjugated        semiconducting polymer such as poly(paraphenylenevinylene) or        polyfluorene. The cathode is typically any material (such as,        e.g., Ca or Ba) that has the ability to inject electrons into        the otherwise empty π*-band of the semiconducting, EL polymer.

The buffer layer is typically a conducting polymer and facilitates theinjection of holes from the anode into the EL polymer layer. The bufferlayer can also be called a hole-injection layer, a hole transport layer,or may be characterized as part of a bilayer anode. Typical conductingpolymers employed as buffer layers include polyaniline (PANI) andpolydioxythiophenes such as poly(3,4-ethylenedioxythiophene) (PEDT).These materials can be prepared by polymerizing the correspondingmonomers in aqueous solution in the presence of a water solublepolymeric acid, such as poly(styrenesulfonic acid) (PSS).

The aqueous electrically conductive polymer dispersions synthesized withwater soluble polymeric sulfonic acids have undesirable low pH levels.The low pH can contribute to decreased stress life of an EL devicecontaining such a buffer layer, and contribute to corrosion within thedevice. Accordingly, there is a need for compositions and buffer layersprepared therefrom having improved properties.

Electrically conducting polyanilines are typically prepared bypolymerizing aniline or substituted aniline monomers in aqueous solutionby an oxidative polymerization using an oxidizing agent such as ammoniumpersulfate (APS), sodium persulfate or potassium persulfate. The aqueoussolution contains a water soluble polymeric acid such aspoly(2-acrylamido-2-methyl-1-propanesulfonic acid) (“PAAMPSA”), PSS, andthe like. In general, enough of the acid is present to form acid/basesalts with emeraldine base of polyanilines, wherein formation of theacid/base salt renders the polyanilines electrically conductive. Thus,for example, emeraldine base of polyaniline (PANI) is typically formedwith PAAMPSA to resulting in electrically conductive PANI/PAAMPSA.

Aqueous polyaniline dispersions are commercially available from OrmeconChemie GmbH and Co. KG (Ammersbeck, Germany). It is known as D1005 WLED. The polyaniline is made from aniline and water solublepoly(styrenesulfonic acid). The dried films obtained from D1005 W LEDre-disperse readily in water. The water becomes acidic with pH in therange of 1 at 2.5% (w/w). Films gain about 24.0% (w/w) moisture atambient conditions.

Dried films from a lab batch aqueous dispersion ofpolyaniline/poly(2-acrylamido-2-methyl-1-propanesulfonic acid), are alsoreadily re-dispersible in water. The polyaniline is made from anilineand a water soluble PAAMPSA.

Electrically conducting polymers also have utility as electrodes forelectronic devices, such as thin film field effect transistors. In suchtransistors, an organic semiconducting film is present between sourceand drain electrodes. To be useful for the electrode application, theconducting polymers and the liquids for dispersing or dissolving theconducting polymers have to be compatible with the semiconductingpolymers and the solvents for the semiconducting polymers to avoidre-dissolution of either conducting polymers or semiconducting polymers.The electrical conductivity of the electrodes fabricated from theconducting polymers should be greater than 10 S/cm (where S is areciprocal ohm). However, the electrically conducting polyaniline madewith a polymeric acid typically provide conductivity in the range of˜10⁻³ S/cm or lower. In order to enhance conductivity, conductiveadditives may be added to the polymer. However, the presence of suchadditives can deleteriously affect the processability of theelectrically conducting polyaniline. Accordingly, there is a need forimproved conductive polyaniline with good processability and increasedconductivity.

SUMMARY OF THE INVENTION

In one embodiment of the invention, compositions are provided comprisingaqueous dispersions of polyaniline and at least one colloid-formingpolymeric acids. The invention compositions are useful as buffer layersin a variety of organic electronic devices, such as organic lightemitting diodes (OLEDs). Invention compositions are also useful incombination with conductive fillers, such as metal nanowires or carbonnanotubes, in applications such as drain, source, or gate electrodes inthin film field effect transistors.

In accordance with another embodiment of the invention, there areprovided organic electronic devices, including electroluminescentdevices, comprising buffer layers of the invention compositions that arecast.

In accordance with still another embodiment of the invention, there areprovided methods for synthesizing aqueous dispersions of polyaniline andat least one colloid-forming polymeric acid.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a cross-sectional view of an electronic device thatincludes a buffer layer according to the invention.

FIG. 2 illustrates a cross-sectional view of a thin film field effecttransistor that includes an electrode according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the invention, compositions are provided comprisingaqueous dispersions of polyaniline and colloid-forming polymeric acids.As used herein, the term “dispersion” refers to a continuous liquidmedium containing a suspension of minute particles. In accordance withthe invention, the “continuous medium” is typically an aqueous liquid,e.g., water. As used herein, the term “aqueous” refers to a liquid thatis at least about 40% by weight water. As used herein, the term“colloid” refers to the minute particles suspended in the continuousmedium, said particles having a nanometer-scale particle size. As usedherein, the term “colloid-forming” refers to substances that form minuteparticles when dispersed in aqueous solution, i.e., “colloid-forming”polymeric acids are not water-soluble.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of the “a” or “an” are employed to describe elements andcomponents of the invention. This is done merely for convenience and togive a general sense of the invention. This description should be readto include one or at least one and the singular also includes the pluralunless it is obvious that it is meant otherwise.

It has been discovered that aqueous dispersions of electricallyconductive poly(anilines) can be prepared when aniline monomers arepolymerized chemically in the presence of colloid-forming polymericacids. Further, it has been discovered that use of a polymeric acid thatis not water soluble in preparation of an aqueous dispersion of thepoly(anilines) yields a composition with superior electrical properties.One advantage of these aqueous dispersions is that the electricallyconductive minute particles are stable in the aqueous medium withoutforming a separate phase over a long period of time before a use.Moreover, they generally do not re-disperse once dried into films.

Compositions according to the invention contain a continuous aqueousphase in which the polyaniline and colloid-forming polymeric acid aredispersed. Polyaniline contemplated for use in the practice of thepresent invention is derived from aniline monomers having Formula Ibelow.

where in Formula I:

n is an integer from 0 to 4;

m is an integer from 1 to 5, with the proviso that n+m=5; and

R¹ is independently selected so as to be the same or different at eachoccurrence and is selected from alkyl, alkenyl, alkoxy, cycloalkyl,cycloalkenyl, alkanoyl, alkylthio, aryloxy, alkylthioalkyl, alkylaryl,arylalkyl, amino, alkylamino, dialkylamino, aryl, alkylsulfinyl,alkoxyalkyl, alkylsulfonyl, arylthio, arylsulfinyl, alkoxycarbonyl,arylsulfonyl, carboxylic acid, halogen, cyano, or alkyl substituted withone or more of sulfonic acid, carboxylic acid, halo, nitro, cyano orepoxy moieties; or any two R¹ groups together may form an alkylene oralkenylene chain completing a 3, 4, 5, 6, or 7-membered aromatic oralicyclic ring, which ring may optionally include one or more divalentnitrogen, sulfur or oxygen atoms.

The polymerized material comprises aniline monomer units, each of theaniline monomer units having a formula selected from Formula II belowand Formula III.

where n, m, and R¹ are as defined above.

Colloid-forming polymeric acids contemplated for use in the practice ofthe invention are insoluble in water, and form colloids when dispersedinto an aqueous medium. The polymeric acids typically have a molecularweight in the range of about 10,000 to about 4,000,000. In oneembodiment, the polymeric acids have a molecular weight of about 100,000to about 2,000,000. Colloid particle size typically ranges from 2nanometers (nm) to about 140 nm. In one embodiment, the colloids have aparticle size of 2 nm to about 30 nm. Any polymeric acid that iscolloid-forming when dispersed in water is suitable for use in thepractice of the invention. In one embodiment, the colloid-formingpolymeric acid is polymeric sulfonic acid. Other acceptable polymericacids include polymeric phosphoric acids, polymeric carboxylic acids,polymeric acrylic acids, and mixtures thereof, including mixtures havingpolymeric sulfonic acids. In another embodiment, the polymeric sulfonicacid is fluorinated. In still another embodiment, the colloid-formingpolymeric sulfonic acid is perfluorinated. In yet another embodiment,the colloid-forming polymeric sulfonic acid is aperfluoroalkylenesulfonic acid.

In still another embodiment, the colloid-forming polymeric acid is ahighly-fluorinated sulfonic acid polymer (“FSA polymer”). “Highlyfluorinated” means that at least about 50% of the total number ofhalogen and hydrogen atoms in the polymer are fluorine atoms, and it oneembodiment at least about 75%, and in another embodiment at least about90%. In another embodiment, the polymer is perfluorinated. The term“sulfonate functional group” refers to either to sulfonic acid groups orsalts of sulfonic acid groups, and in one embodiment alkali metal orammonium salts. The functional group is represented by the formula —SO₃Xwhere X is a cation, also known as a “counterion”. X may be H, Li, Na, Kor N(R₁)(R₂)(R₃)(R₄), and R₁, R₂, R₃, and R₄ are the same or differentand are in one embodiment H, CH₃ or C₂H₅. In one embodiment, X is H, inwhich case the polymer is said to be in the “acid form”. X may also bemultivalent, as represented by such ions as Ca⁺⁺, and Al⁺⁺⁺. It is clearto the skilled artisan that in the case of multivalent counterions,represented generally as M^(n+), the number of sulfonate functionalgroups per counterion will be equal to the valence “n”.

In one embodiment, the FSA polymer comprises a polymer backbone withrecurring side chains attached to the backbone, the side chains carryingcation exchange groups. Polymers include homopolymers or copolymers oftwo or more monomers. Copolymers are typically formed from anonfunctional monomer and a second monomer carrying the cation exchangegroup or its precursor, e.g., a sulfonyl fluoride group (—SO₂F), whichcan be subsequently hydrolyzed to a sulfonate functional group. Forexample, copolymers of a first fluorinated vinyl monomer together with asecond fluorinated vinyl monomer having a sulfonyl fluoride group(—SO₂F) can be used. Possible first monomers include tetrafluoroethylene(TFE), hexafluoropropylene, vinyl fluoride, vinylidine fluoride,trifluoroethylene, chlorotrifluoroethylene, perfluoro(alkyl vinylether), and combinations thereof. TFE is a preferred first monomer.

Possible second monomers include fluorinated vinyl ethers with sulfonatefunctional groups or precursor groups which can provide the desired sidechain in the polymer. Additional monomers, including ethylene,propylene, and R—CH═CH₂ where R is a perfluorinated alkyl group of 1 to10 carbon atoms, can be incorporated into these polymers if desired. Thepolymers may be of the type referred to herein as random copolymers,that is copolymers made by polymerization in which the relativeconcentrations of the comonomers are kept as constant as possible, sothat the distribution of the monomer units along the polymer chain is inaccordance with their relative concentrations and relative reactivities.Less random copolymers, made by varying relative concentrations ofmonomers in the course of the polymerization, may also be used. Polymersof the type called block copolymers, such as that disclosed in EuropeanPatent Application No. 1 026 152 A1, may also be used.

In one embodiment, the FSA polymers for use in the present inventioninclude a highly fluorinated, including those that are perfluorinated,carbon backbone and side chains represented by the formula—(O—CF₂CFR_(f))_(a)—O—CF₂CFR′_(f)SO₃Xwherein Rf and R′f are independently selected from F, Cl or aperfluorinated alkyl group having 1 to 10 carbon atoms, a=0, 1 or 2, andX is H, Li, Na, K or N(R1)(R2)(R3)(R4) and R1, R2, R3, and R4 are thesame or different and in one embodiment are H, CH₃ or C₂H₅. In anotherembodiment X is H. As stated above, X may also be multivalent.

The preferred FSA polymers include, for example, polymers disclosed inU.S. Pat. No. 3,282,875 and in U.S. Pat. Nos. 4,358,545 and 4,940,525.An example of preferred FSA polymer comprises a perfluorocarbon backboneand the side chain represented by the formula—O—CF₂CF(CF₃)—O—CF₂CF₂SO₃Xwhere X is as defined above. FSA polymers of this type are disclosed inU.S. Pat. No. 3,282,875 and can be made by copolymerization oftetrafluoroethylene (TFE) and the perfluorinated vinyl etherCF₂═CF—O—CF₂CF(CF₃)—O—CF₂CF₂SO₂F,perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) (PDMOF),followed by conversion to sulfonate groups by hydrolysis of the sulfonylfluoride groups and ion exchanged as necessary to convert them to thedesired ionic form. An example of a preferred polymer of the typedisclosed in U.S. Pat. Nos. 4,358,545 and 4,940,525 has the side chain—O—CF₂CF₂SO₃X, wherein X is as defined above. This polymer can be madeby copolymerization of tetrafluoroethylene (TFE) and the perfluorinatedvinyl ether CF₂═CF—O—CF₂CF₂SO₂F, perfluoro(3-oxa-4-pentenesulfonylfluoride) (POPF), followed by hydrolysis and further ion exchange asnecessary.

The FSA polymers for use in this invention have an ion exchange ratio ofless than about 33. In this application, “ion exchange ratio” or “IXR”is defined as number of carbon atoms in the polymer backbone in relationto the cation exchange groups. Within the range of less than about 33,IXR can be varied as desired for the particular application. With mostpolymers, the IXR is about 3 to about 33, and in one embodiment about 8to about 23.

The cation exchange capacity of a polymer is often expressed in terms ofequivalent weight (EW). For the purposes of this application, equivalentweight (EW) is defined to be the weight of the polymer in acid formrequired to neutralize one equivalent of sodium hydroxide. In the caseof a sulfonate polymer where the polymer has a perfluorocarbon backboneand the side chain is —O—CF₂—CF(CF₃)—O—CF₂—CF₂—SO₃H (or a salt thereof),the equivalent weight range which corresponds to an IXR of about 8 toabout 23 is about 750 EW to about 1500 EW. IXR for this polymer can berelated to equivalent weight using the formula: 50 IXR+344=EW. While thesame IXR range is used for sulfonate polymers disclosed in U.S. Pat.Nos. 4,358,545 and 4,940,525, e.g., the polymer having the side chain—O—CF₂CF₂SO₃H (or a salt thereof), the equivalent weight is somewhatlower because of the lower molecular weight of the monomer unitcontaining a cation exchange group. For the preferred IXR range of about8 to about 23, the corresponding equivalent weight range is about 575 EWto about 1325 EW. IXR for this polymer can be related to equivalentweight using the formula: 50 IXR+178=EW.

The FSA polymers can be prepared as colloidal aqueous dispersions. Theymay also be in the form of dispersions in other media, examples of whichinclude, but are not limited to, alcohol, water-soluble ethers, such astetrahydrofuran, mixtures of water-soluble ethers, and combinationsthereof. In making the dispersions, the polymer can be used in acidform. U.S. Pat. Nos. 4,433,082, 6,150,426 and WO 03/006537 disclosemethods for making of aqueous alcoholic dispersions. After thedispersion is made, concentration and the dispersing liquid compositionscomposition can be adjusted by methods known in the art.

Aqueous dispersions of the FSA polymers have particle sizes as small aspossible and an EW as small as possible, so long as a stable colloid isformed.

Aqueous dispersions of FSA polymer are available commercially as Nafion®dispersions, from E. I. du Pont de Nemours and Company (Wilmington,Del.).

In accordance with the invention, stable aqueous dispersions areprepared by first synthesizing an electrically conducting polyaniline inthe presence of an aqueous colloid-forming polymeric acid dispersion,thereby forming an as-synthesized aqueous dispersion comprising theelectrically conducting polyanilines and the colloidal polymeric acid.The electrically conducting polyanilines employed in invention methodsare typically prepared by oxidatively polymerizing aniline orsubstituted aniline monomers in an aqueous colloid-forming polymericacid dispersion in the presence of an oxidizing agent, such as ammoniumpersulfate (APS), sodium persulfate, potassium persulfate and the like.The aqueous dispersion contain at least enough of a suitablecolloid-forming polymeric acid to form base/acid salts with theemeraldine base of polyaniline, wherein formation of the acid/base saltrenders the polyanilines electrically conductive.

The method of making an aqueous dispersion of polyaniline and at leastone colloid-forming polymeric acid includes forming a reaction mixtureby combining water, aniline monomer, colloid-forming polymeric acid, andoxidizer, in any order, provided that at least a portion of thecolloid-forming polymeric acid is present when at least one of theaniline monomer and the oxidizer is added.

In one embodiment, the method of making the aqueous dispersion ofpolyaniline and at least one colloid-forming polymeric acid includes:

(a) providing an aqueous dispersion of a colloid-forming polymeric acid;

(b) adding an oxidizer to the dispersion of step (a); and

(c) adding an aniline monomer to the dispersion of step (b).

In another embodiment, the aniline monomer is added to the aqueousdispersion of the colloid-forming polymeric acid prior to adding theoxidizer. Step (b) above, which is adding oxidizing agent, is thencarried out.

In another embodiment, a mixture of water and the aniline monomer isformed, in a concentration typically in the range of about 0.5% byweight to about 2.0% by weight aniline. This aniline mixture is added tothe aqueous dispersion of the colloid-forming polymeric acid, and steps(b) above which is adding oxidizing agent is carried out.

In another embodiment, the aqueous polymerization dispersion may includea polymerization catalyst, such as ferric sulfate, ferric chloride, andthe like. The catalyst is added before the last step. In anotherembodiment, a catalyst is added together with an oxidizing agent.

In one embodiment, the polymerization is carried out in the presence ofco-dispersing liquids which are miscible with water. Examples ofsuitable co-dispersing liquids include, but are not limited to ethers,alcohols, alcohol ethers, cyclic ethers, ketones, nitriles, sulfoxides,amides, and combinations thereof. In one embodiment, the co-dispersingliquid is an alcohol. In one embodiment, the co-dispersing liquid is analcohol selected from n-propanol, isopropanol, t-butanol,dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and mixturesthereof. In general, the amount of co-dispersing liquid should be lessthan about 60% by volume. In one embodiment, the amount of co-dispersingliquid is between 20 and 50% by volume. The use of a co-dispersingliquid in the polymerization significantly reduces particle size andimproves filterability of the dispersions. In addition, buffer materialsobtained by this process show an increased viscosity and films preparedfrom these dispersions are of high quality.

The co-dispersing liquid can be added to the reaction mixture at anypoint in the process prior to the addition of either the oxidizer or theaniline monomer, whichever is added last. In one embodiment, theco-dispersing liquid is added before both the aniline monomer and thecolloid-forming polymeric acid, and the oxidizer is added last. In oneembodiment the co-dispersing liquid is added prior to the addition ofthe aniline monomer and the oxidizer is added last.

In one embodiment, the polymerization is carried out in the presence ofa co-acid which is a Bronsted acid. The acid can be an inorganic acid,such as HCl, sulfuric acid, and the like, or an organic acid, such asacetic acid. Alternatively, the acid can be a water soluble polymericacid such as poly(styrenesulfonic acid),poly(2-acrylamido-2-methyl-1-propanesulfonic acid, or the like, or asecond colloid-forming acid, as described above. Combinations of acidscan be used.

The co-acid can be added to the reaction mixture at any point in theprocess prior to the addition of either the oxidizer or the anilinemonomer, whichever is added last. In one embodiment, the co-acid isadded before both the aniline monomer and the colloid-forming polymericacid, and the oxidizer is added last. In one embodiment the co-acid isadded prior to the addition of the aniline monomer, followed by theaddition of the colloid-forming polymeric acid, and the oxidizer isadded last.

In one embodiment, the polymerization is carried out in the presence ofboth a co-dispersing liquid and a co-acid. Devices with buffer layersmade from polyaniline/Nafion® that was polymerized in the presence of analcohol co-dispersing agent and a co-acid show high efficiencies, lowoperating voltages, low leakage currents and long lifetimes.

In the method of making the aqueous dispersion of polyaniline and atleast one colloid-forming polymeric acid, the molar ratio of oxidizer toaniline monomer is generally in the range of 0.1 to 2.0; and in oneembodiment is 0.4 to 1.5. The molar ratio of colloid-forming polymericacid to aniline monomer is generally in the range of 0.2 to 5. Theoverall solid content is generally in the range of about 1.0% to 6% inweight percentage; and in one embodiment of about 2% to 4.5%. Thereaction temperature is generally in the range of about 4° C. to 40° C.;in one embodiment about 20° C. to 35° C. The molar ratio of optionalco-acid to aniline monomer is about 0.05 to 4. The addition time of theoxidizer influences particle size and viscosity. Thus, the particle sizecan be reduced by slowing down the addition speed. In parallel, theviscosity is increased by slowing down the addition speed. The reactiontime is generally in the range of about 1 to about 30 hours.

As synthesized, the aqueous dispersions of polyaniline and polymericacid colloids generally have a very low pH. It has been found that thepH can be adjusted to typically be between about 1 to about 8, withoutadversely affecting the properties in devices. It is frequentlydesirable to have a pH which is approximately neutral, as the aciditycan be corrosive. It has been found that the pH can be adjusted usingknown techniques, for example, ion exchange or by titration with anaqueous basic solution. Stable dispersions of polyaniline andfluorinated polymeric sulfonic acid colloids with a pH up to 7-8 havebeen formed. Aqueous dispersions of polyaniline and othercolloid-forming polymeric acids can be similarly treated to adjust thepH.

In one embodiment, after completion of the polymerization reaction, theas-synthesized aqueous dispersion is contacted with at least one ionexchange resin under conditions suitable to remove decomposed species,side reaction products, and unreacted monomers, and to adjust pH, thusproducing a stable, aqueous dispersion with a desired pH. In oneembodiment, the as-synthesized aqueous dispersion is contacted with afirst ion exchange resin and a second ion exchange resin, in any order.The as-synthesized aqueous dispersion can be treated with both the firstand second ion exchange resins simultaneously, or it can be treatedsequentially with one and then the other.

Ion exchange is a reversible chemical reaction wherein an ion in a fluidmedium (such as an aqueous dispersion) is exchanged for a similarlycharged ion attached to an immobile solid particle that is insoluble inthe fluid medium. The term “ion exchange resin” is used herein to referto all such substances. The resin is rendered insoluble due to thecrosslinked nature of the polymeric support to which the ion exchanginggroups are attached. Ion exchange resins are classified as cationexchangers or anion exchangers. Cation exchangers have positivelycharged mobile ions available for exchange, typically protons or metalions such as sodium ions. Anion exchangers have exchangeable ions whichare negatively charged, typically hydroxide ions.

In one embodiment, the first ion exchange resin is a cation, acidexchange resin which can be in protonic or metal ion, typically sodiumion, form. The second ion exchange resin is a basic, anion exchangeresin. Both acidic, cation including proton exchange resins and basic,anion exchange resins are contemplated for use in the practice of theinvention. In one embodiment, the acidic, cation exchange resin is aninorganic acid, cation exchange resin, such as a sulfonic acid cationexchange resin. Sulfonic acid cation exchange resins contemplated foruse in the practice of the invention include, for example, sulfonatedstyrene-divinylbenzene copolymers, sulfonated crosslinked styrenepolymers, phenol-formaldehyde-sulfonic acid resins,benzene-formaldehyde-sulfonic acid resins, and mixtures thereof. Inanother embodiment, the acidic, cation exchange resin is an organicacid, cation exchange resin, such as carboxylic acid, acrylic orphosphorous cation exchange resin. In addition, mixtures of differentcation exchange resins can be used.

In another embodiment, the basic, anionic exchange resin is a tertiaryamine anion exchange resin. Tertiary amine anion exchange resinscontemplated for use in the practice of the invention include, forexample, tertiary-aminated styrene-divinylbenzene copolymers,tertiary-aminated crosslinked styrene polymers, tertiary-aminatedphenol-formaldehyde resins, tertiary-aminated benzene-formaldehyderesins, and mixtures thereof. In a further embodiment, the basic,anionic exchange resin is a quaternary amine anion exchange resin, ormixtures of these and other exchange resins.

The first and second ion exchange resins may contact the as-synthesizedaqueous dispersion either simultaneously, or consecutively. For example,in one embodiment both resins are added simultaneously to anas-synthesized aqueous dispersion of an electrically conducting polymer,and allowed to remain in contact with the dispersion for at least about1 hour, e.g., about 2 hours to about 20 hours. The ion exchange resinscan then be removed from the dispersion by filtration. The size of thefilter is chosen so that the relatively large ion exchange resinparticles will be removed while the smaller dispersion particles willpass through. Without wishing to be bound by theory, it is believed thatthe ion exchange resins quench polymerization and effectively removeionic and non-ionic impurities and most of unreacted monomer from theas-synthesized aqueous dispersion. Moreover, the basic, anion exchangeand/or acidic, cation exchange resins renders the acidic sites morebasic, resulting in increased pH of the dispersion. In general, aboutone to five grams of ion exchange resin is used per gram ofpolyaniline/polymeric acid colloid.

In many cases, the basic ion exchange resin can be used to adjust the pHto the desired level. In some cases, the pH can be further adjusted withan aqueous basic solution such as a solution of sodium hydroxide,ammonium hydroxide, tetra-methylammonium hydroxide, or the like.

In one embodiment, a reaction vessel is charged first with a mixture ofwater, alcohol co-dispersing agent, and inorganic co-acid. To this isadded, in order, an aniline monomer, and an aqueous dispersion offluorinated polymeric sulfonic acid colloids, and an oxidizer. Theoxidizer is added slowly and dropwise to prevent the formation oflocalized areas of high ion concentration which can destabilize the acidcolloids. The mixture is stirred and the reaction is then allowed toproceed at a controlled temperature. When polymerization is completed,the reaction mixture is treated with a strong acid cation resin, stirredand filtered; and then treated with a base anion exchange resin, stirredand filtered. Alternative orders of addition can be used, as discussedabove.

In another embodiment, more conductive dispersions are formed by theaddition of highly conductive additives to the aqueous dispersions ofpolyaniline and the colloid-forming polymeric acid. Because dispersionswith relatively high pH can be formed, the conductive additives,especially metal additives, are not attacked by the acid in thedispersion. Moreover, because the polymeric acids are colloidal innature, having the surfaces predominately containing acid groups,electrically conducting polyaniline is formed on the colloidal surfaces.Because of this unique structure, only a low weight percentage of highlyconductive additives is needed to reach the percolation threshhold.Examples of suitable conductive additives include, but are not limitedto metal particles and nanoparticles, nanowires, carbon nanotubes,graphite fibers or particles, carbon particles, and combinationsthereof.

In another embodiment of the invention, there are provided buffer layerscast from aqueous dispersions comprising polymeric aniline andcolloid-forming polymeric acids. In one embodiment, the buffer layersare cast from aqueous dispersions comprising colloid-forming polymericsulfonic acid. In one embodiment, the buffer layer is cast from anaqueous dispersion containing polyaniline and fluorinated polymeric acidcolloids. In another embodiment, the fluorinated polymeric acid colloidsare fluorinated polymeric sulfonic acid colloids. In still anotherembodiment, the buffer layer is cast from an aqueous dispersioncontaining polyaniline and perfluoroethylenesulfonic acid colloids.

The dried films of polyaniline and polymeric acid colloids, such asfluorinated polymeric sulfonic acid colloids, are generally notredispersible in water. Thus the buffer layer can be applied as multiplethin layers. In addition, the buffer layer can be overcoated with alayer of different water-soluble or water-dispersible material withoutbeing damaged.

In another embodiment, there are provided buffer layers cast fromaqueous dispersions comprising polymeric aniline and colloid-formingpolymeric acids blended with other water soluble or dispersiblematerials. Examples of types of materials which can be added include,but are not limited to polymers, dyes, coating aids, organic andinorganic conductive inks and pastes, charge transport materials,crosslinking agents, and combinations thereof. The other water solubleor dispersible materials can be simple molecules or polymers. Examplesof suitable polymers include, but are not limited to, conductivepolymers such as polythiophenes, polyanilines, polypyrroles,polyacetylenes, and combinations thereof.

In another embodiment of the invention, there are provided electronicdevices comprising at least one electroactive layer (usually asemiconductor conjugated polymer) positioned between two electricalcontact layers, wherein at least one of the layers of the deviceincludes the buffer layer of the invention. As shown in FIG. 1, atypical device has an anode layer 110, a buffer layer 120, anelectroluminescent layer 130, and a cathode layer 150. Adjacent to thecathode layer 150 is an optional electron-injection/transport layer 140.Between the buffer layer 120 and the cathode layer 150 (or optionalelectron injection/transport layer 140) is the electroluminescent layer130.

The device may include a support or substrate (not shown) that can beadjacent to the anode layer 110 or the cathode layer 150. Mostfrequently, the support is adjacent the anode layer 110. The support canbe flexible or rigid, organic or inorganic. Generally, glass or flexibleorganic films are used as a support. The anode layer 110 is an electrodethat is more efficient for injecting holes compared to the cathode layer150. The anode can include materials containing a metal, mixed metal,alloy, metal oxide or mixed oxide. Suitable materials include the mixedoxides of the Group 2 elements (i.e., Be, Mg, Ca, Sr, Ba, Ra), the Group11 elements, the elements in Groups 4, 5, and 6, and the Group 8-10transition elements. If the anode layer 110 is to be light transmitting,mixed oxides of Groups 12, 13 and 14 elements, such as indium-tin-oxide,may be used. As used herein, the phrase “mixed oxide” refers to oxideshaving two or more different cations selected from the Group 2 elementsor the Groups 12, 13, or 14 elements. Some non-limiting, specificexamples of materials for anode layer 110 include, but are not limitedto, indium-tin-oxide (“ITO”), aluminum-tin-oxide, gold, silver, copper,and nickel. The anode may also comprise an organic material such aspolyaniline, polythiophene, or polypyrrole. The IUPAC number system isused throughout, where the groups from the Periodic Table are numberedfrom left to right as 1-18 (CRC Handbook of Chemistry and Physics,81^(st) Edition, 2000).

The anode layer 110 may be formed by a chemical or physical vapordeposition process or spin-cast process. Chemical vapor deposition maybe performed as a plasma-enhanced chemical vapor deposition (“PECVD”) ormetal organic chemical vapor deposition (“MOCVD”). Physical vapordeposition can include all forms of sputtering, including ion beamsputtering, as well as e-beam evaporation and resistance evaporation.Specific forms of physical vapor deposition include rf magnetronsputtering and inductively-coupled plasma physical vapor deposition(“IMP-PVD”). These deposition techniques are well known within thesemiconductor fabrication arts.

Usually, the anode layer 110 is patterned during a lithographicoperation. The pattern may vary as desired. The layers can be formed ina pattern by, for example, positioning a patterned mask or resist on thefirst flexible composite barrier structure prior to applying the firstelectrical contact layer material. Alternatively, the layers can beapplied as an overall layer (also called blanket deposit) andsubsequently patterned using, for example, a patterned resist layer andwet chemical or dry etching techniques. Other processes for patterningthat are well known in the art can also be used. When the electronicdevices are located within an array, the anode layer 110 typically isformed into substantially parallel strips having lengths that extend insubstantially the same direction.

The buffer layer 120 is usually cast onto substrates using a variety oftechniques well-known to those skilled in the art. Typical castingtechniques include, for example, solution casting, drop casting, curtaincasting, spin-coating, screen printing, inkjet printing, and the like.Alternatively, the buffer layer can be patterned using a number of suchprocesses, such as ink jet printing.

The electroluminescent (EL) layer 130 may typically be a conjugatedpolymer, such as poly(paraphenylenevinylene), abbreviated as PPV, orpolyfluorene. The particular material chosen may depend on the specificapplication, potentials used during operation, or other factors. The ELlayer 130 containing the electroluminescent organic material can beapplied from solutions by any conventional technique, includingspin-coating, casting, and printing. The EL organic materials can beapplied directly by vapor deposition processes, depending upon thenature of the materials. In another embodiment, an EL polymer precursorcan be applied and then converted to the polymer, typically by heat orother source of external energy (e.g., visible light or UV radiation).

Optional layer 140 can function both to facilitate electroninjection/transport, and can also serve as a confinement layer toprevent quenching reactions at layer interfaces. More specifically,layer 140 may promote electron mobility and reduce the likelihood of aquenching reaction if layers 130 and 150 would otherwise be in directcontact. Examples of materials for optional layer 140 include, but arenot limited to, metal-chelated oxinoid compounds (e.g., Alq₃ or thelike); phenanthroline-based compounds (e.g.,2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (“DDPA”),4,7-diphenyl-1,10-phenanthroline (“DPA”), or the like); azole compounds(e.g., 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (“PBD” orthe like), 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole(“TAZ” or the like); other similar compounds; or any one or morecombinations thereof. Alternatively, optional layer 140 may be inorganicand comprise BaO, LiF, Li₂O, or the like.

The cathode layer 150 is an electrode that is particularly efficient forinjecting electrons or negative charge carriers. The cathode layer 150can be any metal or nonmetal having a lower work function than the firstelectrical contact layer (in this case, the anode layer 110). As usedherein, the term “lower work function” is intended to mean a materialhaving a work function no greater than about 4.4 eV. As used herein,“higher work function” is intended to mean a material having a workfunction of at least approximately 4.4 eV.

Materials for the cathode layer can be selected from alkali metals ofGroup 1 (e.g., Li, Na, K, Rb, Cs), the Group 2 metals (e.g., Mg, Ca, Ba,or the like), the Group 12 metals, the lanthanides (e.g., Ce, Sm, Eu, orthe like), and the actinides (e.g., Th, U, or the like). Materials suchas aluminum, indium, yttrium, and combinations thereof, may also beused. Specific non-limiting examples of materials for the cathode layer150 include, but are not limited to, barium, lithium, cerium, cesium,europium, rubidium, yttrium, magnesium, samarium, and alloys andcombinations thereof.

The cathode layer 150 is usually formed by a chemical or physical vapordeposition process. In general, the cathode layer will be patterned, asdiscussed above in reference to the anode layer 110. If the device lieswithin an array, the cathode layer 150 may be patterned intosubstantially parallel strips, where the lengths of the cathode layerstrips extend in substantially the same direction and substantiallyperpendicular to the lengths of the anode layer strips. Electronicelements called pixels are formed at the cross points (where an anodelayer strip intersects a cathode layer strip when the array is seen froma plan or top view).

In other embodiments, additional layer(s) may be present within organicelectronic devices. For example, a layer (not shown) between the bufferlayer 120 and the EL layer 130 may facilitate positive charge transport,band-gap matching of the layers, function as a protective layer, or thelike. Similarly, additional layers (not shown) between the EL layer 130and the cathode layer 150 may facilitate negative charge transport,band-gap matching between the layers, function as a protective layer, orthe like. Layers that are known in the art can be used. In addition, anyof the above-described layers can be made of two or more layers.Alternatively, some or all of inorganic anode layer 110, the bufferlayer 120, the EL layer 130, and cathode layer 150, may be surfacetreated to increase charge carrier transport efficiency. The choice ofmaterials for each of the component layers may be determined bybalancing the goals of providing a device with high device efficiencywith the cost of manufacturing, manufacturing complexities, orpotentially other factors.

The different layers may have any suitable thickness. Inorganic anodelayer 110 is usually no greater than approximately 500 nm, for example,approximately 10-200 nm; buffer layer 120, is usually no greater thanapproximately 250 nm, for example, approximately 50-200 nm; EL layer130, is usually no greater than approximately 1000 nm, for example,approximately 50-80 nm; optional layer 140 is usually no greater thanapproximately 100 nm, for example, approximately 20-80 nm; and cathodelayer 150 is usually no greater than approximately 100 nm, for example,approximately 1-50 nm. If the anode layer 110 or the cathode layer 150needs to transmit at least some light, the thickness of such layer maynot exceed approximately 100 nm.

Depending upon the application of the electronic device, the EL layer130 can be a light-emitting layer that is activated by signal (such asin a light-emitting diode) or a layer of material that responds toradiant energy and generates a signal with or without an appliedpotential (such as detectors or voltaic cells). Examples of electronicdevices that may respond to radiant energy are selected fromphotoconductive cells, photoresistors, photoswitches, biosensors,phototransistors, and phototubes, and photovoltaic cells. After readingthis specification, skilled artisans will be capable of selectingmaterial(s) that are suitable for their particular applications. Thelight-emitting materials may be dispersed in a matrix of anothermaterial, with or without additives, or form a layer alone. The EL layer130 generally has a thickness in the range of approximately 50-500 nm.

In organic light emitting diodes (OLEDs), electrons and holes, injectedfrom the cathode 150 and anode 110 layers, respectively, into the ELlayer 130, form negative and positively charged polarons in the polymer.These polarons migrate under the influence of the applied electricfield, forming a polaron exciton with an oppositely charged species andsubsequently undergoing radiative recombination. A sufficient potentialdifference between the anode and cathode, usually less thanapproximately 12 volts, and in many instances no greater thanapproximately 5 volts, may be applied to the device. The actualpotential difference may depend on the use of the device in a largerelectronic component. In many embodiments, the anode layer 110 is biasedto a positive voltage and the cathode layer 150 is at substantiallyground potential or zero volts during the operation of the electronicdevice. A battery or other power source(s) may be electrically connectedto the electronic device as part of a circuit but is not illustrated inFIG. 1.

OLEDs provided with buffer layers cast from aqueous dispersionscomprising polymeric aniline and colloid-forming polymeric acids havebeen found to have improved lifetimes. The buffer layer may be cast froman aqueous dispersion of polyaniline and fluorinated polymeric sulfonicacid colloids; and in one embodiment the an aqueous dispersion is one inwhich the pH has been adjusted to above about 3.5.

Using a less acidic or pH neutral material leads to significantly lessetching of the ITO layer during device fabrication and hence much lowerconcentration of In and Sn ions diffusing into the polymer layers of theOLED. Since In and Sn ions are suspected to contribute to reducedoperating lifetime this is a significant benefit.

The lower acidity also reduces corrosion of the metal components of thedisplay (e.g. electrical contact pads) during fabrication and over thelong-term storage. PANI/PSSA residues will interact with residualmoisture to release acid into the displays with resulting slowcorrosion.

The buffer layers of the invention have lower moisture uptake and thusless water is included in the device fabrication process. This lowermoisture level can also result in better operating lifetime for thedevice and reduced corrosion.

Equipment used to dispense the acidic PANI/PSSA needs to be speciallydesigned to handle the strong acidity of PANI/PSSA. For example, achrome-plated slot-die coating-head used to coat the PANI/PSSA onto ITOsubstrates was found to be corroding due to the acidity of thePANI/PSSA. This rendered the head unusable since the coated film becamecontaminated with particles of chrome. Also, certain ink-jet print headsare of interest for the fabrication of OLED displays. They are used fordispensing both the buffer layer and the light-emitting polymer layer inprecise locations on the display. These print-heads contain nickel meshfilters as an internal trap for particles in the ink. These nickelfilters are decomposed by the acidic PANI/PSSA and rendered unusable.Neither of these corrosion problems will occur with the aqueous PANIdispersions of the invention in which the acidity has been lowered.

Furthermore, certain light-emitting polymers are found to be sensitiveto acidic conditions, and their light-emitting capability is degraded ifthey are in contact with an acidic buffer layer. It is advantageous touse the aqueous PANI dispersions of the invention to form the bufferlayer because of the lower acidity or neutrality.

The fabrication of full-color or area-color displays using two or moredifferent light-emitting materials becomes complicated if eachlight-emitting material requires a different cathode material tooptimize its performance. Display devices are made up of a multiplicityof pixels which emit light. In multicolor devices there are at least twodifferent types of pixels (sometimes referred to as sub-pixels) emittinglight of different colors. The sub-pixels are constructed with differentlight-emitting materials. It is very desirable to have a single cathodematerial that gives good device performance with all of the lightemitters. This minimizes the complexity of the device fabrication. Ithas been found that a common cathode can be used in multicolor deviceswhere the buffer layer is made from the aqueous PANI dispersions of theinvention while maintaining good device performance for each of thecolors. The cathode can be made from any of the materials discussedabove; and may be barium, overcoated with a more inert metal such asaluminum.

Other organic electronic devices that may benefit from having one ormore layers comprising the aqueous dispersion of polyaniline and atleast one colloid-forming polyermic acids include (1) devices thatconvert electrical energy into radiation (e.g., a light-emitting diode,light emitting diode display, or diode laser), (2) devices that detectsignals through electronics processes (e.g., photodetectors (e.g.,photoconductive cells, photoresistors, photoswitches, phototransistors,phototubes), IR detectors), (3) devices that convert radiation intoelectrical energy, (e.g., a photovoltaic device or solar cell), and (4)devices that include one or more electronic components that include oneor more organic semi-conductor layers (e.g., a transistor or diode).

The buffer layer can further be overcoated with a layer of conductivepolymer applied from aqueous solution or solvent. The conductive polymercan facilitate charge transfer and also improve coatability. Examples ofsuitable conductive polymers include, but are not limited to,polyanilines, polythiophenes, polythiophene-polymeric-acid-colloids suchas those disclosed in co-pending application Dupont number PE 0688, orpolythiophene/polystyrenesulfonic acid, polypyrroles, polyacetylenes,and combinations thereof.

In yet another embodiment of the invention, there are provided thin filmfield effect transistors comprising electrodes comprising polyanilineand colloid-forming polymeric sulfonic acids. For use as electrodes inthin film field effect transistors, the conducting polymers and theliquids for dispersing or dissolving the conducting polymers must becompatible with the semiconducting polymers and the solvents for thesemiconducting polymers to avoid re-dissolution of either conductingpolymers or semiconducting polymers. Thin film field effect transistorelectrodes fabricated from conducting polymers should have aconductivity greater than 10 S/cm. However, electrically conductingpolymers made with water soluble polymeric acids only provideconductivity in the range of ˜10⁻³ S/cm or lower. Thus, in oneembodiment, the electrodes comprise polyaniline and fluorinatedcolloid-forming polymeric sulfonic acids in combination with electricalconductivity enhancers such as nanowires, carbon nanotubes, or the like.In still another embodiment, the electrodes comprise polyniline andcolloid-forming perfluoroethylenesulfonic acid in combination withelectrical conductivity enhancers such as nanowires, carbon nanotubes,or the like. Invention compositions may be used in thin film fieldeffect transistors as gate electrodes, drain electrodes, or sourceelectrodes.

Thin film field effect transistors, as shown in FIG. 2, are typicallyfabricated in the following manner. A dielectric polymer or dielectricoxide thin film 210 has a gate electrode 220 on one side and drain andsource electrodes, 230 and 240, respectively, on the other side. Betweenthe drain and source electrode, an organic semiconducting film 250 isdeposited. Invention aqueous dispersions containing nanowires or carbonnanotubes are ideal for the applications of gate, drain and sourceelectrodes because of their compatibility with organic based dielectricpolymers and semiconducting polymers in solution thin film deposition.Since the invention conducting compositions, e.g., PANI and colloidalperfluoroethylene sulfonic acid, exist as a colloidal dispersion, lessweight percentage of the conductive fillers is required (relative tocompositions containing water soluble polymeric sulfonic acids) to reachpercolation threshold for high electrical conductivity.

In still another embodiment of the invention, there are provided methodsfor producing, aqueous dispersions of polyaniline comprisingpolymerizing aniline monomers in the presence of polymeric acidcolloids. In another embodiment, the colloid-forming polymeric acid iscarboxylic acid, acrylic acid, sulfonic acid, phosphoric acid, or thelike, or combination of above. In one embodiment of the inventionmethods, the polyaniline is a polyaniline and the colloid-formingpolymeric acid is fluorinated. In another embodiment of the inventionmethods, the polyaniline is unsubstituted polyaniline and thecolloid-forming polymeric acid is perfluorinated. In still anotherembodiment, the colloid-forming acid is polyethylenesulfonic acid. Instill another embodiment, the polyethylenesulfonic acid isperfluorinated. The polymerization is carried out in water. In stillanother embodiment, the perfluoroethylenesulfonic acid containingpolymerization is carried out with an additional acid as set forthabove. The resulting reaction mixture can be treated with ion exchangeresins to remove reaction byproducts and attainment of a desired pHaqueous dispersion. In another embodiment, the pH can be furtheradjusted with ion exchangers or a basic aqueous solution.

The invention will now be described in greater detail by reference tothe following non-limiting examples.

EXAMPLES Comparative Example 1

This comparative example illustrates high moisture uptake, andre-dispersibility of dried solids prepared from D 005 W OLD of OrmeconCompany. It also illustrates acidity of the water in contact with thedried films.

D1005 W LED purchased from Ormecon Chemie GmbH and Co. KG (Ammersbeck,Germany) is aqueous polyaniline dispersion. The polyaniline polymer wasproduced from the polymerization of aniline and a water solublepoly(styrenesulfonic acid). About 15 ml of the aqueous dispersion wasdried with a flowing stream of nitrogen. 0.05 g of the dried polymerfilms was mixed with 0.45 g deionized water having a pH of 7. The pH wasmeasured with a piece of Color pHast.® indicator strip (EM Science, pH0-14 range, Cat #9590). The color of the wet strip was compared with thecolor chart for reading of pH. As soon as the polymer films were incontact with the de-ionized water, the water turned dark green and soonlater dispersed completely in the water. PH of the water was about 1,which is very acidic. The dried film also picked up about 24% moistureat ambient conditions (˜25′C/50% RH). This example illustrates thatpolyaniline made with a water soluble polymeric acid disperses readilyin water forming a low pH of dispersion. It also picks up a substantialamount of moisture. All the results show that the acid is very mobileand has high propensity of migrating into adjacent polymer layers, suchas light polymer layer, to damage their function.

Comparative Example 2

This comparative example illustrates re-dispersibility of dried solidsprepared from an aqueous PAni/PAAMPSA dispersion in which the dispersedpolyaniline is made with aniline and a water soluble PAAMSA. It alsoillustrates acidity of the aqueous dispersion.

60.65 g (43.90 mmoles of acid monomer units) aqueous PAAMPSA solution(Aldrich, Cat #19, 197-3, lot #07623EO, M_(w)˜2 million, 15% solid inwater) was introduced into a jacketed 500 ml three-necked flask,followed by 335.07 g de-ionized water. The flask was equipped with astirring paddle powered by an air-driven overhead stirrer and a smalltube for adding ammonium persulfate. The small tube was placed inside aglass pipette with the tip removed and the pipette was inserted througha 29 size septa so that the end of the tube extended out of the pipetteapproximately ½″ above the reaction mixture. A thermocouple with aninlet for monitoring the temperature of the polymerization liquid in thejacketed flask was used to keep circulation of the fluid at 22° C. Afterstirring of the PAAMPSA/water mixture commenced, freshly distilledaniline (4.0 mL, 43.9 mmoles) was added to the flask via a transferpipette. The mixture was allowed to mix with stirring for approximatelyone hour. While stirring continued, ammonium persulfate (4.01 g, 17.572mmoles, 99.999+% pure from Aldrich) was massed into a scintillationvial, and the mass was mixed with 16.38 g de-ionized water. This mixturewas placed in a Norm-Ject 30 ml syringe, which was connected to the tubein the flask using a 17-gauge syringe needle. The syringe was connectedto a Harvard Apparatus 44 Syringe Pump programmed to add the ammoniumpersulfate (APS) over 30 minutes. During the addition of APS,temperature of the mixture was about 23° C. The reaction mixture turnedblue one minute after addition of APS began and started to darken. Afteraddition of the APS solution was completed, the reaction was allowed toproceed for 24 hours with constant stirring.

After 24 hours, the reaction mixture was poured into a 4 L plasticNalgen® beaker, agitation from the overhead stirrer was started, andacetone (2000 L) was poured into the 4 L beaker. Stirring of the acetonemixture continued for 30 minutes. Once stirring was stopped, the mixturewas allowed to settle into two layers. Most of the reddish-yellow liquidphase was decanted, leaving behind a tarry solid product, which was thentransferred to an Erlenmeyer flask. The flask was positioned in such away that the stirring blade could be used for agitation. Another 430 mlof fresh acetone was quickly added to the beaker. This was allowed tostir for 15 minutes. This produced slurry, which was allowed to standfor about 30 minutes before being suctioned filtered through a Buchnerfunnel equipped with one piece of Whatman #54 filter paper. The motherliquid was clear and colorless. Another 430 ml of fresh acetone wasquickly added to the product. This was allowed to stir for approximately90 minutes. This slurry was allowed to stand for about four hours beforebeing suction-filtered through a Buchner funnel equipped with one pieceof Whitman #54 filter paper. while a greenish solid product collected onthe filter paper. The filtrate had a very light green color associatedwith it. The filtered cake had fine particles, but a few large sizeparticles. The funnel and its contents were placed into a vacuum oven(˜20 inch mercury, ambient temperature) for about two days. Yield was11.93 g.

0.31 g of the PAni/PAAMPSA powder made above was mixed with 20.38 gdeionized water. The polymer powder dispersed in the water very quicklyto form 1.5% (w/w) dispersion. 1.5 g of the dispersion was mixed with3.0 g de-ionized water for pH test using a piece of Color pHast.®indicator strip described above. pH of the dispersion is about 3. Thisexample illustrates that polyaniline made with a water soluble polymericacid disperses readily in water forming a low pH of dispersion. Theresults show that the acid is very mobile and has propensity ofmigrating into adjacent polymer layers, such as light polymer layer, todamage their function.

Example 1

This example illustrates preparation of an aqueous PAni/Nafion®dispersion in which the dispersed polyaniline is made with aniline andNafion®, a colloidal perfluoroethylenesulfonic acid. This example alsoillustrates non-dispersibility and low moisture uptake of the driedsolids prepared from the aqueous PAni/Nafion® dispersion. It alsoillustrates neutrality of the water in contact with the dried films.

A Nafion® polymer dispersion made according to the method described inU.S. Pat. No. 6,150,426 patent issued in Nov. 21, 2000 was used in thisinvention. The Nafion® polymer dispersion sample contains 12.0% (w/w)perfluoroethylenesulfonic acid colloids in water and the Nafion® polymerhas 1050 g/mole of monomer unit of acid. 191.63 g (21.90 mmoles ofNafion® monomer units) of the Nafion® polymer dispersion and 206.32 gde-ionized water were poured into a jacketed 500 ml three-necked flask.The flask was equipped with a stirring paddle powered by an air-drivenoverhead stirrer and a small tube for ammonium persulfate. The smalltube was placed inside of a glass pipette with the tip removed. This wasput through a 29 size Septa so that the tube was extended out of thepipette approximately ½″ above the reaction mixture. A thermal couplehas its own inlet for monitoring temperature of polymerization liquid inthe jacketed flask allowing circulation of 20° C. fluid. Stirring of theNafion®/water mixture then commenced. 2.0 ml (21.9 mmoles aniline)distilled aniline was then added via a transfer pipette. This wasallowed to stir for a period of approximately one hour. While stirring,2.02 g (8.852 mmoles) ammonium persulfate (99.999+% pure from Aldrich)was massed into a Scintillation Vial. The mass was then mixed with 8.16g deionized water. This was then sucked into a Norm-Ject 30 ml syringe,which was hooked to the aforementioned tube using a 17-gauge syringeneedle. The syringe was hooked to a Harvard Apparatus 44 Syringe Pump.The Syringe Pump was set up in such way that the ammonium persulfate(APS) was added in 30 minutes, but actual addition time was 28 minutes.During the polymerization, temperature was about 20° C. The reactionmixture was very foamy and turned blue within 20 minutes of APSaddition. Within one hour, the polymerization was already very dark incolor and appeared to be very homogeneous. The polymerization wasallowed to proceed for about 25 hours and the entire content ofpolymerization liquid was poured into a 1 liter Erlenmeyer flask.

The polymerization liquid is dark green in color, expected color forelectrically conducting polyaniline. The liquid was left un-disturbedfor 44 hours. It was surprised to discover that the polymerizationliquid did not separate into two phases, meaning a clear liquid layer onthe top and green precipitate on the bottom. This result clearly showsthat a stable aqueous dispersion of polyaniline/Nafion® has been made.

The polymerization liquid was then suction-filtered through a BuchnerFunnel containing two pieces of Whatman #54 filter paper. When thefiltrate started to go through, it was dark green in color and becameless color due to blinding of the filter paper. The filtration becameextremely slow, therefore filter paper had to be changed several times.The collected filter cake, while still wet, was re-dispersed in 400 mlde-ionized water. Filtration was done in the same manner and thecollected filtration cake, while still wet, was re-dispersed in 300 mldeionized water.

Portion of the 300 ml PAni/Nafion* dispersion was left undisturbed forone week. Once again, there is no separation of the dispersion into aclear liquid phase although there were some green precipitates on thebottom. Portion of the dispersion was dried with a flowing stream ofnitrogen to form solid films for solid percentage. It was determined tobe 3.2%. The dried films were then ground into fine powder, which isvery dark green. TGA shows that the dried powder only picks up 1.7%moisture while equilibrating at 25° C./50% RH.

0.1255 g of the PAni/Nafion® powder was mixed with 4.8770 g de-ionized,neutral water and stirred with a shaker. The PAni/Nafion® polymer powderremains intact without discoloring the water. pH of the water remainsneutral when tested with a piece of pHastt® litmus paper. This resultclearly shows that the polymeric aid remains in the polymer even incontact with water, which remains neutral.

Example 2

This example illustrates preparation of an aqueous PAni/Nafion®dispersion and effect of resin treatment on dispersion stability and pH.This example also illustrates non-dispersibility and low moisture uptakeof the dried solids prepared from the aqueous PAni/Nafion® dispersion.It also illustrates neutrality of the water in contact with the driedfilms.

In this invention example, SE10072 Nafion® was used for polymerizationwith aniline. The Nafion® is commercially available from E. I. Dupont deNemours & Company, Delaware, USA. Nafion® in SE10072 has colloid size inthe range of 40 nm to 140 nm as opposed to the Nafion® used in inventionExample 1, which has colloid size in the range of 2 to 30 nm cited inU.S. Pat. No. 6,150,426 patent issued in Nov. 21, 2000.

The polymerization procedure described in invention Example 1 for makingPAni/Nafion® was followed closely. A SE 10072 Nafion® colloidaldispersion used in this example contains 11.2% (w/w)perfluoroethylenesulfonic acid colloids in water. The Nafion® polymerhas about 920 g/mole of monomer unit of acid. 97.29 g (11.84 mmoles ofNafion® monomer units) of the Nafion® dispersion and 296.15 g de-ionizedwater were poured into a jacketed 500 ml three-necked flask. Stirring ofthe Nafion®/water mixture then commenced while 20° C. fluid wascirculated continuously through the jacketed flask. 1.079 ml (11.84mmoles) distilled aniline was then added to the flask via a transferpipette. This was allowed to stir for a period of one hour. Whilestirring, 1.08 g (4.73 mmoles) ammonium persulfate (99.999+% pure fromAldrich) was massed into a Scintillation Vial. The mass was then mixedwith 4.38 g deionized water. The ammonium persulfate solution was addedto the reaction mixture in 34 minutes. During the polymerization,temperature was about 20.4° C. The reaction mixture was foamy. Withinone hour, the polymerization was already very dark green in color andappeared to be inhomogeneous. A small drop of the polymerization wasplaced on a microscope slide, which formed a very rough film once dried.The polymerization was allowed to proceed for about 24.5 hours. Thepolymerization liquid was emptied from the reactor to two plasticbottles. One portion weighed 184 g; the other weighed 203 g. The 184 gportion was left standing overnight. It separated into two layers. Thetop layer is clear liquid, but the bottom layer is dark greenprecipitation.

The 203 g portion of the polymerization liquid was mixed with 7.69 gDowex® 550A and 7.94 g Dowex® 66 were added to the reaction flask andleft stirred for 20 hours. Dowex 550A is a quaternary amine anionexchange resin and Dowex®66 is a tertiary amine ion exchange resin (DowChemical Company, MI). The resins were washed repeatedly with deionizedwater until there was no color or odor in the water washings prior touse. The resin-treated slurry was then pre-filtered through a CheeseCloth directly into a 1-liter beaker. A second filtration was donethrough a 500-mesh stainless steel. The filtrate was stable and could gothrough 0.45-micron dp filter (Whatman 25 mm GDX, Catalog number:6992-2504). The pH of the filtered dispersion was measured with a pHmeter model 63 from Jenco Electronics, Inc. and was found to be 7.4. Theresin-treatment evidently rendered the PAni/Nafion® polymerizationliquid into a stable dispersion. It should be also understood that pH ofthe polymerization liquid can be adjusted from ˜1.5 to any pH belowneutrality depending on amount of ion exchange resins used andresin-treatment time. 1.5 is typical pH for the liquid derived from thepolymerization of 1 mole aniline/1 mole Nafion®/0.4 mole ammoniumpersulfate,

A small portion of the resin-treated PAni/Nafion® was dried with flowingnitrogen until a constant weight. It was then left equilibrated atambient room temperature to absorb moisture. Moisture uptake wasdetermined to be 3.6%. The dried solid did not re-disperse in water andthe water in contact with the solid had a ph of 7, measured with a pHmeter model 63 from Jenco Electronics, Inc.

Example 3

This example illustrates preparation of a high pH aqueous PAni/Nafion®dispersion and device properties.

In this invention example, SE10072 Nafion® was used for polymerizationwith aniline. The Nafion® is commercially available from E. I. Dupont deNemours & Company, Delaware, USA. The Nafion® in SE10072 has colloidsize in the range of 40 nm to 140 nm as opposed to the Nafion® used ininvention Example 1, which has colloid size in the range of 2 to 30 nmcited in U.S. Pat. No. 6,150,426 patent issued in Nov. 21, 2000.

The polymerization procedure described in invention Example 1 for makingPAni/Nafion® was followed closely. A SE10072 Nafion® colloidaldispersion used in this example contains 11.2% (w/w)perfluoroethylenesulfonic acid colloids in water. The Nafion® polymerhas about 920 g/mo1e.of monomer unit of acid. 194.6 g (23.69 mmoles ofNafion® monomer units) of the Nafion® dispersion and 602.28 g de-ionizedwater were poured into a jacketed one liter three-necked flask. Stirringof the Nafion®/water mixture then commenced while 20° C. fluid wascirculated continuously through the jacketed flask. 2.159 ml (23.69mmoles) distilled aniline was then added to the flask via a transferpipette. This was allowed to stir for a period of one hour. Whilestirring, 2.18 g (9.553 mmoles) ammonium persulfate (99.999+% pure fromAldrich) was massed into a Scintillation Vial. The mass was then mixedwith 8.74 g deionized water. The ammonium persulfate solution was addedto the reaction mixture in 30 minutes. During the polymerization,temperature was about 20.4° C. The reaction mixture was very foamy.Within one hour, the polymerization was already very dark green in colorand appeared to be very homogeneous. The polymerization was allowed toproceed for about 24 hours. 18.82 g Dowex® 550A and 14.88 g Dowex® 66were added to the reaction flask and left stirred for 4.4 hours. Dowex550A is a quaternary amine anion exchange resin and Dowex®66 is atertiary amine ion exchange resin (Dow Chemical Company, MI). The resinswere washed repeatedly with deionized water until there was no color orodor in the water washings prior to use. The resin-treated slurry wasthen pre-filtered through a Cheese Cloth directly into a 1-liter beaker.A second filtration was done through a 500-mesh stainless steel. Yield:670.80 g.

About 30 ml of the dispersion sample prepared above was filtered through0.45 micron dp filter (Whatman 25 mm GDX, Catalog number: 6992-2504).The pH of the filtered dispersion was measured with a pH meter model 63from Jenco Electronics, Inc. and was found to be 7.4.

For light emission measurement, the aqueous PAni/Nafion® dispersionhaving pH of 7.2 was spin-coated onto ITO/glass substrates at a spinningspeed of 800 rpm to yield a thickness of 1000 Å. The PAni/Nafion®coatedITO/glass substrates were dried in nitrogen at 90° C. for 30 minutes.The PAni/Nafion® layers were then top-coated with a super-yellow emitter(PDY 131), which is a poly(substituted-phenylene vinylene) (CovionCompany, Frankfurt, Germany). The thickness of the electroluminescent(EL) layer was approximately 70 nm. Thickness of all films was measuredwith a TENCOR500 Surface Profiler. For the cathode, Ba and Al layerswere vapor-deposited on top of the EL layers under a vacuum of 1×10⁻⁶torr. The final thickness of the Ba layer was 30 Å; the thickness of theAl layer was 3000 Å. Device performance was tested as follows. Currentvs. voltage, light emission intensity vs. voltage, and efficiency weremeasured with a 236 source-measure unit (Keithley) and a S370 Optometerwith a calibrated silicon photodiode (UDT Sensor). One light-emittingdevice showed an operating voltage of 3.65 volt and light emissionefficiency is 7.2 Cd/A (Cd: candela; A: amperage) light emissionefficiency at 200 Cd/m².

Example 4

92.00 g of DI water and 92.00 g of 99.7% n-propanol were massed directlyinto a 500 mL double-jacketed reactor vessel at room temperature. Next,3.58 mL (43.59 mmol) of 37% wt. HCl and 1.988 mL (21.80 mmol) of aniline(distilled) were added to the reactor via pipet. The mixture was stirredoverhead with a U-shaped stir-rod set at 500 RPM. After five minutes,91.98 g (10.90 mmol) of water-dispersed Nafion® (DE-1020, 10.9% solids,920 EW) that had been passed through a 0.3 μm profile filter, was addedslowly via glass funnel. The mixture was allowed to homogenize for anadditional five minutes. 1.99 g (8.72 mmol) of ammonium persulfate(99.99+%) dissolved in 20 g of DI water was added drop wise to thereactants via syringe infusion pump over one hour. Eight minutes laterthe solution turned light turquoise. The solution progressed to beingdark blue before turning very dark green. After the APS addition began,the mixture was stirred for 90 minutes and 7.00 g of Amberlyst-15 (Rohmand Haas Co., Philadelphia, Pa.) cation exchange resin (rinsed multipletimes with a 32% n-propanol (in DI water) mixture and dried undernitrogen) was added and the stirring commenced overnight at 200 RPM. Thenext morning, the mixture was filtered through steel mesh and stirredwith Amberjet 4400 (OH) (Rohm and Haas Co., Philadelphia, Pa.) anionexchange resin (rinsed multiple times with a 32% n-propanol (in DIwater) mixture and dried under nitrogen) until the pH had changed from0.9 to 4.4. The resin was again filtered off. Before use, the dispersionwas filtered through a 0.45 μm Millipore Millex-HV syringe filter withPVDF membrane. Yield: approximately 300 g dispersion with 4% solids in32% n-propanol/68% DI water.

The dispersions were spun onto glass at 1600 RPM, resulting in filmshaving a thickness of 1151 Å. The conductivity was 1.36×10⁻⁵ S/cm

Devices were made as described in Example 3. The devices had theperformance given below, where t_(1/2) is the time of continuousoperation after which the brightness is one-half the initial brightness,at the temperature indicated:

-   -   voltage and efficiency at 600 cd/m²: 3.45 V and 9.8 cd/A;    -   leakage current at −7V: 2 μA;    -   T_(l/2) at 80° C. (initial brightness: 412 cd/m²): 97 hrs.

Example 5

88.11 g of 99.7% n-propanol and 88.11 g of DI water were massed directlyinto a 500 mL double-jacketed reactor vessel at room temperature. Next,0.167 mL (2.0 mmol) of 37% wt. HCl and 0.901 mL (9.9 mmol) of aniline(distilled) were added to the reactor via pipet. The mixture was stirredoverhead with a U-shaped stir-rod set at 500 RPM. After five minutes,100.03 g (11.90 mmol) of water-dispersed Nafion® (DE-1020, 11.1% solids,935 EW) that had been passed through a 0.3 μm profile filter, was addedslowly via glass funnel. The mixture was allowed to homogenize for anadditional 10 minutes. 2.82 g (12.4 mmol) of ammonium persulfate(99.99+%) dissolved in 20 g of DI water was added drop wise to thereactants via syringe infusion pump over six hours. Seven minutes laterthe solution turned light turquoise. The solution progressed to beingdark blue before turning very dark green. After the APS addition began,the mixture was stirred for 360 minutes and 7.50 g of Amberlyst-15cation exchange resin (rinsed multiple times with a 32% n-propanol (inDI water) mixture and dried under nitrogen) was added and the stirringcommenced overnight at 200 RPM. The next morning, the mixture wasfiltered through steel mesh and stirred with Amberjet 4400 (OH) anionexchange resin (rinsed multiple times with a 32% n-propanol (in DIwater) mixture and dried under nitrogen) until the pH had changed from1.3 to 4.8. The resin was again filtered off. Before use, the dispersionwas filtered through a 0.45 μm Millipore Millex-HV syringe filter withPVDF membrane. Yield: approximately 270 g dispersion with 4% solids in31% n-propanol/69% DI water.

The dispersions were spun onto glass at 1000 RPM, resulting in filmshaving a thickness of 2559 Å. The conductivity was 1.67×10⁻⁶ S/cm.

Devices were made as described in Example 3. The devices had thefollowing performance:

-   -   voltage and efficiency at 600 cd/m²: 3.56 V and 10.3 cd/A;    -   leakage current at −7V: 6 μA;    -   T_(1/2) at 80° C. (initial brightness: 490 cd/m²): 148 hrs.

While the invention has been described in detail with reference tocertain preferred embodiments thereof, it will be understood thatmodifications and variations are within the spirit and scope of thatwhich is described and claimed.

1. A method of making an aqueous dispersion of polyaniline and at leastone colloid-forming fluorinated sulfonic acid polymeric acid includingthe step of forming a combination of water, aniline monomer,colloid-forming fluorinated sulfonic acid polymeric acid, and oxidizer,in any order, provided that at least a portion of the colloid-formingfluorinated sulfonic acid polymeric acid is present when at least one ofthe aniline monomer and the oxidizer is added.
 2. A method according toclaim 1 wherein said aniline monomer has Formula I

wherein: n is an integer from 0 to 4; m is an integer from 1 to 5, withthe proviso that n+m=5; and R¹ is independently selected so as to be thesame or different at each occurrence and is selected from alkyl,alkenyl, alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkythio, aryloxy,alkylthioalkyl, alkylaryl, arylalkyl, amino, alkylamino, dialkylamino,aryl, alkylsulfinyl, alkoxyalkyl, alkylsulfonyl, arylthio, arylsulfinyl,alkoxycarbonyl, arylsulfonyl, carboxylic acid, halogen, cyano, or alkylsubstituted with one or more of sulfonic acid, carboxylic acid, halo,nitro, cyano or epoxy moieties; or any two R¹ groups together may forman alkylene or alkenylene chain completing a 3, 4, 5, 6, or 7-memberedaromatic or alicyclic ring, which ring may optionally include one ormore divalent nitrogen, sulfur or oxygen atoms.
 3. A method according toclaim 2 wherein m is
 5. 4. A method according to claim 1 wherein saidpolymeric acid is a perfluorinated sulfonic acid.
 5. A method accordingto claim 4, wherein said polymeric acid is perfluoroethylenesulfonicacid.
 6. A method according to claim 1, wherein the oxidizer is selectedfrom ammonium persulfate, sodium persulfate, potassium persulfate, andmixtures thereof.
 7. A method according to claim 1, wherein thecombination further comprises a catalyst.
 8. A method according to claim7, wherein the catalyst is selected from ferric sulfate, ferricchloride, and mixtures thereof.
 9. A method according to claim 1,wherein the combination further comprises a co-dispersing liquid.
 10. Amethod according to claim 9, wherein the co-dispersing liquid isselected from ethers, alcohols, alcohol ethers, cyclic ethers, ketones,nitriles, sulfoxides, amides, and combinations thereof.
 11. A methodaccording to claim 10, wherein the combination further comprises aco-acid.
 12. A method according to claim 9, wherein the co-dispersingliquid is selected from n-propanol, isopropanol, t-butanol,dimethylacetamide, dimethylformamide, N-methylpyrrolidone, andcombinations thereof.
 13. A method according to claim 1, wherein thecombination further comprises a co-acid.
 14. A method according to claim13, wherein the co-acid is selected from a water-soluble inorganic acid,a water-soluble organic acid, a colloid-forming polymeric acid, andcombinations thereof.
 15. A method according to claim 1, wherein themethod further comprises contacting a reaction product with at least oneion exchange resin.
 16. A method according to claim 15, wherein said atleast one ion-exchange resin is selected from a cation exchange resin,anionic exchange resin, and mixtures thereof.
 17. A method according toclaim 15, wherein the aqueous dispersion is contacted with a cationexchange resin and then with an anionic exchange resin.
 18. A methodaccording to claim 16, wherein the cation ion exchange resin is selectedfrom sulfonated styrene-divinylbenzene copolymers, sulfonatedcrosslinked styrene polymers, phenol-formaldehyde-sulfonic acid resins,benzene-formaldehyde-sulfonic acid resins, and mixtures thereof; and theanionic exchange resin is selected from tertiary-aminatedstyrene-divinylbenzene copolymers, tertiary-aminated crosslinked styrenepolymers, tertiary-aminated phenol-formaldehyde resins,tertiary-aminated benzene-formaldehyde resins, and mixtures thereof. 19.A method according to claim 17, wherein the cation ion exchange resin isselected from sulfonated styrene-divinylbenzene copolymers, sulfonatedcrosslinked styrene polymers, phenol-formaldehyde-sulfonic acid resins,benzene-formaldehyde-sulfonic acid resins, and mixtures thereof; and theanionic exchange resin is selected from tertiary-aminatedstyrene-divinylbenzene copolymers, tertiary-aminated crosslinked styrenepolymers, tertiary-aminated phenol-formaldehyde resins,tertiary-aminated benzene-formaldehyde resins, and mixtures thereof.